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Fri, 03 Oct 2025 06:31:04 -0700 (PDT) Received: from fedora ([45.116.149.225]) by smtp.gmail.com with ESMTPSA id 41be03b00d2f7-b6099f72c54sm4627884a12.45.2025.10.03.06.31.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 03 Oct 2025 06:31:03 -0700 (PDT) From: rtapadia730@gmail.com To: dsterba@suse.com, clm@fb.com, fdmanana@kernel.org Cc: linux-btrfs@vger.kernel.org, linux-kernel@vger.kernel.org, skhan@linuxfoundation.org, khalid@kernel.org, david.hunter.linux@gmail.com, Rajeev Tapadia Subject: [PATCH v2] btrfs: fix comment in alloc_bitmap() and drop stale TODO Date: Fri, 3 Oct 2025 19:00:02 +0530 Message-ID: <20251003133001.45052-2-rtapadia730@gmail.com> X-Mailer: git-send-email 2.51.0 Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Rajeev Tapadia All callers of alloc_bitmap() hold a transaction handle, so GFP_NOFS is needed to avoid deadlocks on recursion. Update the comment and drop the stale TODO. Signed-off-by: Rajeev Tapadia Reviewed-by: Filipe Manana --- Change log: As per previous review the change is not required. So just removing the stale TODO. fs/btrfs/free-space-tree.c | 8 +++----- 1 file changed, 3 insertions(+), 5 deletions(-) diff --git a/fs/btrfs/free-space-tree.c b/fs/btrfs/free-space-tree.c index dad0b492a663..bb8ca7b679be 100644 --- a/fs/btrfs/free-space-tree.c +++ b/fs/btrfs/free-space-tree.c @@ -165,11 +165,9 @@ static unsigned long *alloc_bitmap(u32 bitmap_size) =20 /* * GFP_NOFS doesn't work with kvmalloc(), but we really can't recurse - * into the filesystem as the free space bitmap can be modified in the - * critical section of a transaction commit. - * - * TODO: push the memalloc_nofs_{save,restore}() to the caller where we - * know that recursion is unsafe. + * into the filesystem here. All callers hold a transaction handle + * open, so if a GFP_KERNEL allocation recurses into the filesystem + * and triggers a transaction commit, we would deadlock. */ nofs_flag =3D memalloc_nofs_save(); ret =3D kvzalloc(bitmap_rounded_size, GFP_KERNEL); --=20 2.51.0